Intravascular catheters are widely used in the medical field as they provide advantages over the various types of needles which were previously used. In particular, where medical treatment requires either continuous or else quick and easy access to an intravascular site the use of a catheter is often the preferred mode of treatment.
While catheters provide many advantages for vascular access, one significant problem remains. The primary problem with catheters is the fact that the removal of the inner needle creates an open passageway for the retrograde flow of blood out through the catheter and its hub.
The procedure for removing the needle from the catheter requires the physician, or other health personnel, to withdraw the needle with one hand while the other hand stabilizes and/or further inserts the catheter in the vessel, usually by holding the hub. Thus, the physician must withdraw the needle, put it down and seize the male connector of the tube, syringe or similar item, which will be secured within the hub of the catheter, and make the connection. Up until the time the connection is made it is common to experience retrograde blood flow out of the catheter. The greatest concern relative to this blood flow is of course the possibility of transmitting diseases such as hepatitis or Acquired Immune Deficiency Syndrome (AIDS) to the attending health personnel. Of a lesser, though still significant degree, is the extremely detrimental effect that seeing this loss of blood has upon the patient. Depending upon the emotional stability of the patient and their experiences in this area the range of emotions can go anywhere from mild annoyance to virtual hysteria which, depending upon the patient's other conditions, could cause a severe reaction. Of a less severe nature is the fact that the blood often stains the patient's clothing, bedding and the like which requires the patient to be moved as these items are changed.
In an attempt to avoid these problems many physicians will attempt to hold the male connector in the same hand which is being used during the withdrawal of the needle to accomplish a quicker insertion of the male adapter into the catheter hub. The practice of this procedure will generally enable the physician to accomplish this transfer with only a small loss of blood due to retrograde flow, however, even a small loss of blood can be dangerous if the blood is contaminated. Specifically, the needle which is withdrawn, and perhaps contaminated, is secured between two fingers, most commonly the ring finger and middle finger, while the sterile connector which is to be inserted into the catheter hub, is held between the thumb and forefinger. As is readily recognizable, minimal control is had over the needle and while attention is being paid to maintaining the connector in a sterile condition and inserting it into the hub, the catheter needle is exposed and being moved which greatly increases the possibility of sticking either the physician or perhaps an attendant nurse who could be restraining the patient or otherwise required to be in close proximity to the treatment site.
Some physicians will remove the needle from the catheter and quickly place it at bed side, or hand it to an attending nurse for disposal, before trying to secure the connector in place. While this method may be preferable to the single handed method discussed above, whatever methods are employed there is always the danger of needle injury while one is connecting the male connector to the catheter.
Clearly, the safest approach is to remove the needle from the catheter and then dispose of it before uncovering the sterile tip of the connector and inserting it into the catheter hub. Such an approach however, is of course not possible unless there is a valve mechanism which will prevent the retrograde flow of blood. To accomplish this, a valve mechanism accommodating both the inner needle and the male connector is required. To fabricate such a valve two important criteria must be considered.
First, size requirements of a catheter make it difficult to fabricate a proper valve mechanism. For example, a valve mechanism would normally be placed within the plastic hub of the catheter the size of which is determined by connectors which are inserted therein. Since the hub is a rather small opening, the valve mechanism is limited in size.
Second, the valve must accommodate an inner needle which is passed through the hub and catheter with the distal end of the needle extending out of the catheter end for insertion into a blood vessel. Then, after the inner needle is removed, the valve must easily accommodate the insertion of a male connector.
Presently available valves, such as cylindrical shaped plugs, ball-ring valves, collapsible tube segment, diaphragm etc. do not meet the above two requirements. Presently only a septum valve could be considered as meeting these requirements. However, the use of a septum as a valve causes other problems.
First, if the septum is not thick enough, upon withdrawal of the needle, the bevel of the needle which is at the distal end, will span the distance from one side of the septum to the other, thus providing an outlet for retrograde blood flow. Furthermore, the septum must be located in the hub in such a way that it can be secured in place. However, securing the septum within the hub by a hinged connection causes a dead space between the septum and the proximal end of the catheter tubing. Upon injection, air caught in the dead space is injected into the person's blood stream which may cause an air embolism depending upon the amount of air and the injection site. Even when the injected air is not dangerous it is discomforting to the patient. Also, whenever a needle is required to pierce a substance, there is the possibility that part of the septum could be cut off and lodged in the bore of the needle. This is especially true if the needle has to be put through the septum more than once as may be the case if the needle is not aligned exactly enough to slide into the catheter tubing.
Compounded with the above difficulties is the fact that after the needle is removed, the valve mechanism must be movable to an open position upon insertion of the male connector from the tube or other device which is to be secured within the hub of the catheter. Since these male connectors are not designed to pierce the septum, the septum must be moved out of the way by some other mechanism.
Thus, these septum valves are generally 2-way, hinged along one side so they open upon insertion of the male connector. Therefor these septums require an additional device such as a plug to prevent the septum from opening in an outward direction due to blood pressure. Furthermore, often, while a catheter is in place, tubes must be changed and the constant insertion and withdrawal of the male connector can loosen the valve, if not secured properly within the hub, thus causing leakage around the sides of the septum or in the worst case, complete removal of the septum upon the withdrawal of the male connector.